I checked a diode pack from a Delco alternator one time and found that the reverse breakdown voltage was at least 120 volts. So, such a diode pack should work fine at 24 volts. You can do it yourself if you can get hold of an oscilloscope. A variac also helps. You also need an isolation transformer and a suitable resistor. Connect the variac to 120 volts ac, and the variable ac output to the primary of the 1:1 isolation transformer. Take the output of the isolation transformer and connect in series with the resistor and the diode under test. Put the scope in X-Y mode and connect the scope ground to the point where the resistor and diode join. Connect one input across the diode and the other across the resistor. Start with the variac output at zero and work your way up. You should be able to ascertain whether reverse breakdown will occur at too low a voltage. The isolation transformer is there to avoid grounding problems. If this all Greek to you, then get yourself a book on circuit theory and read, read, read....
